The invention relates to a process for the production of synthesis gas from a carbon-containing fuel as, for example, all types of coal, coke, petroleum coke, biomass but also emulsions, orimulsion, etc., and the combustion of such synthesis gas for heat and power generation. By the inventive process the synthesis gas can be cleaned easily without any further cooling and its heat and pressure energy first be used for power generation and its chemical energy for power generation using a conventional combined-cycle process. The interconnected treatment of the synthesis gas facilitates the generation of power by an additional turbine without the turbines being damaged by corrosive components. The invention also relates to a contrivance with the aid of which this process can be implemented.
In the production of synthesis gas from a carbon-containing fuel, the fuel reacts with air or oxygen or oxygen-enriched air with a potential content of water vapour in a reactor suited for this purpose. Apart from synthesis gas also mineral slags are obtained in this process, which generally consist of aerosols or droplets. Some of these liquids partly evaporate and form alkali vapours and hydrogen chloride. In most cases these are very disturbing for the further use as they may damage or adversely affect the sections of the downstream process facilities.
For this reason it is advantageous to remove the entrained foreign constituents from the synthesis gas produced. DE 1020 07063118 A1 describes a process for the treatment of a synthesis gas by bringing it into contact with getter ceramics, the synthesis gas being routed without pre-cooling to a slag separation device in which slag droplets are withdrawn as liquid slag. The slag separation device can be of a cyclone type or be a packed bed of an inert material in which the slag separates from the gas.
This type of treatment does not entail cooling or expansion of the synthesis gas so that its pressure and heat energy can be used for driving the expansion turbine. Only then will the synthesis gas be passed to a process which uses the produced synthesis gas in a great variety of ways. The additional turbine facilitates a better use of the pressure and heat energy of the synthesis gas produced so that the efficiency of the process for the generation of power from synthesis gas is considerably improved. The mechanical energy can, for example, be used for the generation of power.
The synthesis gas produced is frequently used for the production of chemical products. However, it is also possible to burn the synthesis gas thus generated and use the produced combustion gas first to drive a gas turbine. This serves for an optimum use of the pressure energy from combustion. The heat of the combustion gas expanded by the turbine is then used for the generation of steam. The steam drives a steam turbine by means of which power can be generated. This process—the simultaneous use of the pressure energy from combustion and the generation of steam for driving a steam turbine—is commonly called a combined-cycle process.
Processes for the production of synthesis gas with the purpose of combustion for the generation of power in a combined-cycle process are already known. U.S. Pat. No. 6,233,916 B1 describes a process for the generation of electric power using the pressure energy of the fuel gas for driving a turbine. The heat of the expanded fuel gas can be used by a system of heat exchangers. The fuel gas may be of any type. It may, for example, be a natural gas or an industrial gas which originates from chemical industry and is passed to combustion. This process involves a better use of the pressure and heat energy of the fuel gas. The process also includes subsequent steam and power generation.
The gas used here must be free of corrosive constituents. However, many industrial gases used for the generation of power contain corrosive constituents. In particular, synthesis gas produced in a coal gasification process still contains a larger amount of molten slag directly downstream of the gasification section and also particularly contains halogenated compounds such as alkali vapours or hydrogen halides. This will cause problems if a turbine installed upstream of the combustion process is used. The corrosive constituents of the synthesis gas can damage the turbine blades, the turbine shaft or the bearings. For this reason, purified gases must be used when using upstream turbines.
However, the treatment of synthesis gas entails a lot of effort. For this purpose, the synthesis gas obtained must be cooled down and passed through a gas scrubber. After gas scrubbing, the treated gas is obtained which must possibly be re-heated for combustion. This involves high costs. In addition, gas scrubbing processes require much equipment.
The aim is therefore to provide a simple method for the treatment of synthesis gas which is integrated in the process. The process for power generation is preferably a combined-cycle process which uses the combustion gases in two stages for power generation. Such units of adequate design are of a high efficiency. The fuel can be used more efficiently when using a coal gasification process. In addition, a larger variety of fuels can be used when using a downstream combustion for the production of synthesis gas.